Serous otitis media (SOM) is a common condition in children and frequently leads to deafness at a critical age of development. The broad objective of this research is to study SOM in order to elucidate the pathogenesis of this condition. The immediate goals of this study are: (1) to establish correlation between levels of bacteria-inhibiting factors (lysozyme and immunoglobulins) and success rate of bacterial culture in the effusions, (2) to clarify role of mucosal secretion in formation of effusions, (3) to devise practical diagnostic laboratory procedures if above correlation is established, and (4) to see if mucosal metaplasia leads to cholesteatoma in SOM. In order to accomplish the above goals, middle ear effusions, mucosal biopsy, and serum from the patient with SOM will be investigated by immunochemistry, cytochemistry, and electron microscopy. In addition, an attempt will be made to test the following hypotheses in animal model: 1. Metaplasia of mucosa following primary infection leads to hypersecretion in subsequent infections. 2. Primary infection produces sensitization of tubal and middle ear mucosa, and the subsequent infection results in immediate and/or delayed hypersensitivity. BIBLIOGRAPHIC REFERENCES: Lim DJ, Liu YS, Birck HG: Secretory lysozyme by the human middle ear mucosa. Ann Otol Rhinol Laryngol 85:50-60, 1976. Lim DJ (Ed): Report of Research Conference on Middle Ear Effusions. Ann Otol Rhinol Laryngol, Suppl 26, Vol 85, 1976.